In order to reverse the direction of the magnetizations of magnetic bodies included in recording media, application of external magnetic fields has been necessary.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-272114    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-272112    Non-patent Document 1: Science, vol. 301, pp. 943-945 (Aug. 15, 2003)